Propagation of trees from cuttings



Patented Mar. 3, 1942 PROPAGATION F TREES FROM CUTTINGS Ralph H. McKee, New York, N. Y., assignor to McKee Poplar Forestation, Inc., New York, N. Y., a corporation of New York a No Drawing. Original application May 21, 1936,

Serial No. 81,075.

Divided and this application July 29, 1939, Serial No. 287,411

14 Claims.

This invention relates to an improved method of propagating trees from cuttings, and more particularly to the propagation from cuttings of certain new hybrid poplars which I have developed.

This is a division of my copending application Serial No. 81,075, filed May 21, 1936.

The principal object of the present invention is to provide improvements in methods of propagating trees from cuttings whereby the number of living trees obtainable from a given number of cuttings may be increased.

A further object of the invention is to provide a method of increasing the viability of cuttings for purposes of propagation.

A further object of the invention is to provide a method of propagating hybrid poplars by a vegetative (asexual) method in order that there may be no variation in the trees produced, as there is when trees are grown from seed, and in order that every tree of one variety will have the same characteristics as every other tree of that variety, and notably the same hardiness and vigor of growth.

Other objects and advantages of the present invention will become apparent during the course of the following description.

It is well known that, over much of the world, wood is being consumed much faster than it is now growing. In the United States the more important species, such as spruce, pine, fir, poplar, etc., are being out several times as fast as they are growing. This is especially true of the species commonly used for pulpwood. For example, because of its long fiber which imparts strength to paper made therewith, spruce wood is used extensively as pulpwood with the result that spruce trees have been extensively cut down in areas adjacent pulp mills and stands of spruce have been located are in inaccessible locations.

In view of a large consumption of spruce wood, and its very slowrate of growth (about 51 of an inch in diameter per year) the availabl American supplies of spruce are within sight of exhaustion.

Due to the cost of spruce wood and its limited supply, it has been customary to employ poplar pulp with spruce pulp in the manufacture of paper. For example, in the manufacture of ordinary book paper, of spruce pulp is used with 80% of poplar pulp. As a result of the in-. creasing consumption of poplar wood in cellulose industries, there is a resulting decreasing supply. Accordingly, it would obviously be desirable to provide abundant sources of poplar wood for future consumption. Moreover, it would be desirable to obtain poplar wood of increased fiber length so that paper of the desired strength could be produced from wood pulp without the necessity for the use of spruce pulp.

However, the trees of the genus Populus now used commercially in the United States for match wood, lumber and pulpwood, notably P. tremuloides, P. tremuloides aurea, P. grandidentata and the yellow poplar (Liriodendron tulipifera) have not been grown successfully from cuttings and, therefore, they have been rarely, if ever, used in forestation. Moreover, several disadvantages attend the forestation with ordinary poplars, such as the slow growth of the trees, insuflicient fiber length of the wood, the rich soil required for maximum growth of the trees, and their susceptibility to numerous common tree diseases.

Therefore, it is apparent that there is a practical need for a method of forestation by which poplar wood, and especially poplar wood of increased fiber length, can be economically and quickly produced on a large scale.

The present invention contemplates forestation with one or more varieties of the new hybrid poplars which I have developed. Numerous varieties of these new hybrid poplar are referred to in my prior Patent No. 1,943,030 (page 2, line 105 ff.) and several of these new hybrid poplars have been described in my Plant Patent No. 207, issued November 17, 1936; Nos. 211-218, issued January 5, 1937; Nos. 225-226, issued January 19, 1937; and Nos. 228-230, issued January 26,

These new hybrid poplars which I have developed possess severalcharacteristics which make them especially suitable for use in forestation and for supplying wood for use as pulpwood. For example, most of the new hybrid poplars root easily and, hence, may be readily propagated from cuttings, sometimes called scions or slips, and the present invention involves the treatment of cuttings'to promote root growth. Ordinarily the viability and hardiness of cuttings from these new hybrid poplars is such that survival can be expected. Due to the remarkable ease of propagating most of these new hybrid poplars, cuttings may be taken and planted throughout the growing season as well as when leaves have fallen in the fall. This is part cularly true when the cuttings are prepared for setting out in the preferred manner hereinafter-described.

As indicated above, the present invention contemplates propagating the new hybrid poplars vegetatively by planting cuttings taken from living trees. If desired, the cuttings can, as is customary, be taken late in the season and stored over the winter for early spring planting. In order to secure optimum results, I prefer to subject the cuttings to certain preliminary treatments before such' cuttings are planted. One method of treating the cuttings to expedite propagation and improve viability is to soak the fresh cuttings in water for say one to three hours and preferably until the cuttings are waterlogged and sink. If instead of merely using water, a fungicide or insecticide suspension or solution is employed. there will be no chance of the cuttings transmitting insect or fungus pests, such as rusts.

After the cuttings have been soaked in water they are preferably then dried on the surface and the tops of the cuttings are then coated with a suitable waterproof coating. If desired,

the tops of the cuttings may be dipped in ordi- I nary paraffin or other suitable wax before planting, as disclosed in my Patent No. 1,943,030. However, I have lately found that if instead of using ordinary paraffin as disclosed in myprior patent, there be used a high melting wax, better results are obtained. A high melting wax gives better adherence in the bark of the cutting and also does not soften when exposed to the sun on a hot summer day. The latter is an important factor since if the wax melts it will often injure the bark of the infant tree. Of the cheap waxes available, the less common commercial paraffin having a melting point above 50 0., say around 55 (3., serves excellently.

In providing the tops of the cuttings with a water-proofing coating, a Wax having a melting point above 50 C. is melted and the upper part of the cutting, say the upper half, is dipped into the melted paraflin and quickly withdrawn. The dipping of the cutting into the melted parafiin should be only for an instant since long contact with the hot material will injure the cutting.

This improved method of providing cuttings with a waterproof coating of a high melting wax permits taking shorter cuttings, say six inches long, and using smaller wood than hitherto, down to say 1% inch diameter. In addition, it is possible to make the cuttings from green, growing wood and then to plant the treated cuttings at once, thereby securing growth immediately and also saving winter storage, as well as greatly lengthening the planting period. These green cuttings, which may be made durtings from a particular hybrid poplar will root well or not, that is, whether the cuttings carry the natural root-producing hormones in quantity or not. I have found that cuttings from certain crosses, notably those with Populus alba as a parent, do not root sufiiciently well to provide a sufiiciently high percentage of survival for commercial operation. However, I have discovered that this disadvantage may be overcome by subjecting the cuttings to a treatment with a solution of hormones whereby root growth will be promoted.

If cuttings of these hybrids are treated with a solution of hormones (phytohormones) in an oil or lanolin or water medium, or alone, root growth will be facilitated. If the cuttings of the previously mentioned hybrid poplars are treated with these phytohormones, root growth will be hastened and intensified. The most practical method of application is to soak the lower part of the cutting in an aqueous solution or finely divided suspension of the root-producing hormones. Such root-producing compounds are generally those having an acidic chain of atoms with a closed ring at one end, of which perhaps the simplest is phenylacetic acid. Other materials of like usefulness are phenylstearic acid (cf. my Patent No. 1,972,568) xylenestearic acid, phenylpropionic acid, alpha or beta-naphthaleneacetic acid, indolebutyric acid, indole-3-N-propionic acid and beta-indoleacetic acid. The above mentioned complex compounds are preferably used in solution at about or C. Urine contains such a phytohormone and may be used instead ing the months of May to September, inclusive,

are so-called soft wood cuttings and have not been calloused. They are cuttings made when the actively growing leaves are on the branches used. However, the leaves should be removed before the cuttings are waxed and planted. Of course, as stated above, cuttings can-be made late in the season and stored over the winter for early spring planting.

In the preferred practice of my present method,

of a solution of one of the complex compounds mentioned above. When urine is used, it is diluted with several times. its volume of water and the cuttings are allowed to stand in this solution at ordinary temperature over night.

Where it is desired to facilitate the root growth of cuttings of the hybrid poplars with which sired, but also the hormones which are intended to promote root growth.

' Of the artificial hormones, the preferred ones are phenylstearic acid and xylenestearic acid, especially the former. Where these or other stimulating acids are to be employed for the purpose of promoting-root growth, I prefer to treat the cuttings with a salt of the selected acid which on exposure to the air or by the action of the soil in which the cuttings are planted will liberate the free acid to be effective as a root stimulant. For example, I may treat the cuttings with an ammonium salt of the stimulating acid which will lose its ammonia on exposure to the air and leave the free acid to act as a root stimulant. Similarly, I may use a sodium or other alkali salt of the selected acid which will, under the action of acidic agents in the soil, set free the acid to be effective to promote root growth.

The preferred method of application is to make an ammonium or sodium soap of phenylstearic or xylenestearic acid and dissolve this in water to give a dilute solution, say 0.5%. After the cutting has been waxed the lower portion of the cutfrom a given number of cutting from the solution and drying superficially,

the ammonia will evaporate from the ammonium soap leaving the free phenylstearic acid. In the case of the sodium soap the water will evaporate leaving a film of the soap on the cutting. When such a cutting is planted in an ordinary soil having a pH of less than 6, as do most forest soils, the acidity of the soil will setfree the phenylstearic acid from its soap and thereby permit it to act to facilitate root growth on the cutting.

To illustrate the eifectiveness of phenylstearic acid in facilitating root growth, an experiment was carried out in which the lower portions of cuttings of a hybrid poplar (that disclosed in my Plant Patent No. 228, with parents P. angulate x P. eugenez') were treated with a solution of phenylstearic acid and planted along with untreated controls of the same hybrid. After some weeks, and before the controls showed a single root, the treated cuttings averaged seventeen (17) vigorous rootlets per cutting.

While the above described preliminary treatments of cuttings prior to planting, i. e. the preliminary soaking of the cuttings, the partial cutting of the cuttings with a waterproofing material such as a high melting point wax, the soaking of the waxed cuttings before planting, and the treatment of cuttings with hormones capable of promoting root growth, may be advantageously employed in the propagation of my new hybrid poplars from cuttings, these treatments are not confined to such specific use. These treatments, by the use of which green cuttings may be employed for propagation and as a result of the use of which the number ofliving trees obtainable cuttings may be increased, are capable of general application in propagating trees from cuttings. For example, the several preliminary treatments may be employed in the propagation from cuttings of pure species 01' poplars, P. tremuloides aurea, P. balsamilera, P. suaveolens, P. Simonii, and willows such as Salim nigra, and black gum, Nz/ssa sylvatica, as well as other species.

While I have described in detail the preferred practice of my method, it is to be understood that the details of procedure may be variously modifled without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. In a method of propagating poplars from cuttings, the improvement which comprises immersing the cuttings in an aqueous medium containing a salt of an acid having a stearic acid chain attached to a ring group of atoms, and planting the treated cuttings.

2. In a method 01! propagating poplars from cuttings, the improvement which comprises immersing the cuttings in an aqueous medium contings,

taining a salt of phenylstearic acid, and planting the treated cuttings.

' 3. In a method of propagating poplars. from cuttings, the improvement which comprises immersing the cuttings in an aqueous medium containing a salt of xylenestearic acid, and planting the treated cuttings.

4. In a method of propagating trees from cutthe improvement for increasing the viability of said cuttings which comprises subjecting said cuttings prior to planting to treatment with an aqueous medium, a hormone capable of stimulating root growth-comprising a salt of an acid having a stearic acid chain attached to a ring group of atoms, and a waterproofing coating material applied to the upper portion of said cuttings.

5. A method in accordance with claim 4 in which said salt is a phenylstearate.

6. A method in accordance with claim 4 in which the cuttings are subjected to treatment with the aqueous medium until they are waterlogged.

7. A method in accordance with claim 4 in which the waterproofing coating material is a molten wax having a melting point above 50 C. 8. A method in accordance with claim 4 in which the cuttings treated are green cuttings taken during the period of from May to September, inclusive.

9. In a method of propagating trees from cuttings, the improvement ior increasing the viability of said cuttings which comprises subjecting said cuttings prior to planting to treatment with an aqueous medium, a salt of phenylstearic acid, and a waterproofing coating'material applied to the upper portion of said cuttings.

10. A method in accordance with'claim 9 in which the cuttings are subjected to treatment with the aqueous medium until they are waterlogged.

11. A method in accordance with claim 9 in which the waterproofing coating material is a molten wax having a melting point above 50 C.

12. A method in accordance with claim 9 in which the cuttings treated are green cuttings taken during the period of from May to September, inclusive.

13. The method of propagating poplars from cuttings which comprises taking green poplar cuttings during the period of from May to September, inclusive, and subjecting said cuttings prior to planting to treatment with an aqueous medium, a salt of phenylstearic acid, and a molten wax applied to the upper portion of said cuttings.

14. A method in accordance with claim 13 in which the cuttings are subjected to treatment with the aqueous medium until they are waterlogged and in which the molten wax has a melting point above 50 C.

RALPH H. MCKEE. 

